A sticky string oozes out of a spigot and forms a customized structure. This scene could either describe the additive manufacturing process called 3D printing or how an arachnid spins its spider web to trap prey. Spider webs are marvels of sustainable engineering. They are intricate structures tailor-made for their environment from a nontoxic, biodegradable material that is remarkably strong, tough and elastic all at once. Scientists study spider webs to develop materials with similar properties for practical applications in medicine, industrial use and aerospace engineering.
What Are Spider Webs Made Of?
There are many different types of webs — for trapping prey, protecting eggs, and more — but they are all made of silk proteins. Specifically, they are made of glycine, alanine and serine, which are amino acids, a.k.a. the molecules that combine to form proteins.
Webs vary in structure and material. Different species make various webs, but even a single spider produces a variety of silk. Some spider silk is sticky, while other silk is waterproof or optimized for the spider to walk on it. Along with versatility, engineers are interested in spider silk for many useful characteristics:
- Strength: It is five times stronger than steel (by weight) and at least as strong as Kevlar.
- Toughness: Although webs appear delicate, they are relatively difficult to damage.
- Elasticity: It can stretch more than rubber and nylon, according to research published in the journal e-Polymers.
- Flexibility: It is more flexible than nylon, per Discovery.
- Stickiness: It is stickier than most tape, as Evolution News explains.
- Temperature resilience: Webs can withstand high and low temperatures, according to e-Polymers.
- Energy absorption: Its static load and impact resistance are better than those of other artificial and natural materials, according to e-Polymers.
Each of these properties is useful, but the unique combination makes spider silk especially intriguing and worth pursuing. Materials engineers can develop novel substances that are strong and flexible, but nobody does it as well as spiders.
How Spiders Spin Webs
The silk starts as a liquid called dope in the spider’s glands. The glands secrete the dope and the spider pushes it through ducts, then through spigots on its spinnerets, which are silk-spinning organs located on its rear abdomen. Similar to the way a 3D printer squeezes plastic through a nozzle, the spider’s spigot has a valve that controls the thickness and speed of the material, so it can customize the web. Finally, the spinnerets wind strands together to form a thread. It is a sophisticated process that humans have struggled to understand and replicate.
Science journalist Katherine J. Wu, Ph.D., writes for the New York Times, “On their way out of a spider’s bottom, the protein building blocks in silk, called spidroins, fold themselves and interlace, creating a highly organized structure without guidance from any outside force.”
There are many types of webs, such as draglines that spiders use to travel, pheromone-laced webs that females use to attract mates, and nursery webs for carrying spiderlings. But the best known is called an orb web. The spider excretes the thread into the air, and it catches on a nearby branch or some other anchor nearby, as HowStuffWorks explains. The first thread becomes a bridge that the spider travels across as it strategically releases threads to form a web. Some strands are sticky enough to trap prey. But the spider also weaves a few strands without an adhesive coating, so they can walk along the web without getting stuck themselves.
Can Humans Use Spider Webs?
People have been using the spider web directly and indirectly for thousands of years. For example, Ancient Greeks and Romans used balled-up webs as bandages, according to Discovery. Spider silk is particularly well suited for medicine because it is non-toxic and absorbable. It could also be a vector for drug delivery and a basis for 3D photodetectors for bioimaging.
Scientists and engineers are exploring industrial applications such as cables, sensors, composite materials and soft robotics. Spider silk also has potential for aerospace, such as for developing shock-absorbing components for rocks or strong and flexible composite materials for aircraft and spacecraft. The possibilities are endless — armor, clothing, art and more.
The trick is spiders don’t make great livestock. It is challenging to extract silk from the spider’s glands due to the complicated process of spinning silk threads and the fact that each spider has several glands that produce a variety of silk types. Plus, you can’t put a bunch of spiders in a cage together; they are carnivorous animals that will eat each other.
Scientists continue to discover what spider webs are made of and how they are made, while also exploring ways to create spider silk, for example, through genetic engineering or synthetic chemistry. Synthetic biology is an emerging research field that could provide a path for artificial spider silk. Until then, humans continue to be inspired by spiders and their ultra-strong sustainable designs.
Are you interested in science and innovation? We are, too. Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery.